Siemens SIMATIC NET 12M Operating Instructions Manual page 8

Introduction
1.2 Description of the product
• 2 switches:
– right-hand switch ("Termination")
– left-hand switch
• A 1.5 m long spur line with a 9-pin D-sub male connector
You can connect a DTE directly to this spur line.
Figure 1-1
Terminal block
Short name
PE
A1
B1
A2
B2
PE
Terminal block
The following is recommended for PROFIBUS:
• Terminal A - green wire
• Terminal B - red wire
Termination
Activate the termination on the first and last node of the bus segment.
If termination is activated (termination on), the connection between the incoming (A1, B1) and
outgoing (A2, B2) segment is interrupted. If the wrong bus terminating resistors are activated,
it is no longer possible to access stations downstream from the bus terminal. When a segment
is put into operation, there must therefore be no bus terminating resistors activated that are not
located at the start or end of the network.
8
With the right-hand switch, you can terminate the end of an incoming, electrical segment
(A1, B1) with the characteristic impedance (switch on). At the same time, the outgoing,
electrical segment (A2, B2) is interrupted.
With the left-hand switch you can set the range of the transmission speed 9.6 kbps... 1.5
Mbps and 3 Mbps...12 Mbps.
Operator controls
Meaning
Protective earth connected to the cable shield and DIN rail
Signal line A of the incoming segment side
Signal line B of the incoming segment side
Signal line of the outgoing segment side
Signal line of the outgoing segment side
Protective earth connected to the cable shield and DIN rail
Operating Instructions, 06/2022, C79000-G8976-C333-02
12M bus terminal